Hospitals stockpiled blood for emergency transfusions, liquor stores were ordered shut, and President John F. Kennedy placed 15,000 paratroopers on alert. The nation's capital was experiencing "the worst case of pre-invasion jitters since the First Battle of Bull Run," Life magazine wrote in August 1963.

The source of the foreboding was the March on Washington for Jobs and Freedom -- the prospect of tens of thousands of black demonstrators converging on the city to press for civil rights.

Nettie Hailes, then 35, was there that Aug. 28 and rejoiced at the sight of blacks and whites singing spirituals and dipping their tired feet in the Reflecting Pool. People nestled in trees for a better view of the steps to the Lincoln Memorial, where the VIPs included the Rev. Martin Luther King Jr., singer Mahalia Jackson and actors Sidney Poitier and Marlon Brando.

Yet Hailes, whose husband, Edward, helped organize the march, also feared that the wrong word, a scuffle -- anything, really -- could trigger mayhem that would tarnish the peaceful images they hoped to project to the world. As the hours wore on and the sun beat down, Hailes found herself closing her eyes and "praying for it to be over and for everything to be okay."

Her worst fears, and those of the authorities, never came to pass. King's "I Have a Dream" speech, delivered to 250,000 marchers on the Mall, gave the civil rights movement a soaring voice and an indelible image, catapulting it to the top of the American political agenda. Police arrested a grand total of four people.

"We tend to remember this as a sunny and upbeat day where the American dream was invoked and everyone dangled their feet in the water of the Reflecting Pool," said historian Taylor Branch, author of "Parting the Waters," a widely acclaimed chronicle of the civil rights movement. "In fact, what made it so memorable was the sharp disparity between the expectations and the way things turned out. The expectation was terror, and the result, comparatively, was a picnic."

It was a day in which Washingtonians set aside their usual routines. Herb Bryan, then 23 and a recent Howard University graduate, put on a suit coat and tie and walked to the Mall from his New Hampshire Avenue fraternity house. Virginia Ali, the owner of Ben's Chili Bowl, left her husband behind to run the restaurant because she felt compelled to be there.

And Ellen Schwartz, a 23-year-old analyst for the National Science Foundation, ignored the pleas of her Boston parents, who feared that the gathering would spin violently out of control.

"All is fine here in Washington," she wrote them immediately after the march, describing the "peaceful hush" that hovered over downtown as the marchers assembled. "One could not help but feel the greatness of the moment," she said in her letter. "It was a testament of the dignity of the goals, to the dignity of a people which had been treated with indignity for centuries."

Before that day, the largest organized protests in the city included a 1925 Ku Klux Klan rally in which 25,000 members in white hoods and robes paraded down Pennsylvania Avenue. In 1932, roughly 20,000 World War I veterans -- the Bonus Marchers, as they were known -- camped out by the Anacostia River to demand money for their service before President Herbert Hoover ordered Gen. Douglas MacArthur to run them out of town.

Black leaders threatened to march in Washington in 1941, but called it off after President Franklin D. Roosevelt promised to enact reforms that led to the integration of the defense industry. By the summer of 1963, with racial violence flaring across the South, A. Philip Randolph renewed talk of a march, an idea King had also begun to envision. A coalition of black leaders met in New York and announced that they would host a mass demonstration Aug. 28 to support the president's civil rights legislation.

The Rev. Walter E. Fauntroy became King's point man in the District. He coordinated everything from parking to the placement of portable toilets and water fountains to printing signs for marchers to carry. Most important, Fauntroy said, was to send a clear signal that the marchers had to be well behaved. "We were afraid that people frightened by possible violence would stay away," he said. "We let it be known that anyone who came to the march and engaged in violence would be known as a traitor to the cause."

Anxiety over the crowds grew until the night before the march, when it was overtaken by a more practical concern. An adviser to Attorney General Robert F. Kennedy telephoned Fauntroy at home, where he was trying to rest, with the bad news: The sound system was not working. Someone had cut the cables.

Repair crews worked through the night, and by late morning, as speakers arrived at the steps of the Lincoln Memorial, the system was back on. "It was a miracle," Fauntroy said.

By then, tens of thousands of marchers were rolling into Washington, delivered by 21 chartered trains and buses that passed through Baltimore, by one count, at the rate of 100 per hour. One participant, Ledger Smith, then 27, a truck driver, roller skated from Chicago.

Herb Bryan and his Alpha Phi Alpha brothers had painted the house and cleaned up for the occasion. He had started working at the U.S. Patent Office, where his white co-workers spoke of taking the day off because they were "worried that things would get out of hand."

As he arrived at the Mall, Bryan said he was overwhelmed by the crowd's size. "I thought, 'Look at them, boy, this is a national thing. People are coming out to be counted, to stand up,' " he said.

By the time King stood at the microphone, introduced as the "moral leader of the nation," many in the throng had been standing in the heat for more than five hours.

Ali, then 30, inched her way toward the front, close enough to see Harry Belafonte in a crowd of stars that included Charlton Heston and Sammy Davis Jr., who told a reporter that day, "We're not here as celebrities. We are Negroes, and we have a stake in this."

She said tears rolled down her cheeks as King spoke of Mississippi as "a state sweltering in the heat of injustice," and of Alabama Gov. George C. Wallace, "his lips dripping with the words of interposition and nullification."

Nettie Hailes, halfway back along the Reflecting Pool, craned her neck as King spoke of transforming "the jangling discords of our nation into a beautiful symphony of brotherhood."

"Free at last!" King chanted. "Free at last! Thank God Almighty, we are free at last!"

As King stepped from the podium and the crowd cheered, Hailes knew that she had just witnessed history. Just as important, she knew that the day was over and that everything had turned out okay.

President Abraham Lincoln's statue at the Lincoln Memorial overlooked a crowd of 250,000 during the march that Aug. 28.Despite fears of violence before the 1963 March on Washington for Jobs and Freedom, it turned out to be safe for young and old alike. Police arrested only four people.Virginia Ali and Herb Bryan remember leaving their usual Washington routines and heading to the Mall to attend the march.